1. Technical Field
The present invention relates to an air bag inflator, and particularly to an inflator for inflating an air bag to protect the driver of a vehicle.
2. Description of the Prior Art
An inflator for a vehicle air bag commonly includes an igniter having igniter material which ignites when the igniter is actuated. Ignition of the igniter material ignites gas generating material. The gas generating material, when ignited, generates gas for inflating the air bag. The gas generating material typically ignites and burns at a temperature of about 650.degree. F. or higher.
The inflator may on occasion be subjected to abnormally high temperatures. For example, if a vehicle is involved in a fire, the temperatures in the vehicle adjacent the inflator may reach or exceed 650.degree. F. In such a situation, the gas generating material might be at a high enough temperature to ignite.
To avoid ignition of the gas generating material when the ambient vehicle temperature is excessively high, a quantity of auto ignition material is located within the inflator or the igniter. The auto ignition material is specifically designed to ignite at a lower temperature than the temperature at which the gas generating material ignites. The common auto ignition materials ignite at around 350.degree. F. When the auto ignition material ignites, the gas generating material is ignited. Thus, the gas generating material is ignited when the ambient temperature is about 350.degree. F. U.S. Pat. No. 4,561,675 discloses an air bag inflator including an auto ignition material. U.S. Pat. No. 4,858,951 discloses auto ignition material incorporated in an igniter used in the primary ignition train for an air bag inflator.